"Buying an lcd or dmd matrix-based projector often comes with some strange behavior. All of a sudden, the owner gets the desire of "scaling" everything. That's just fine as this is exactly what offers the application Dscaler, previously known as dTV. Dscaler can be installed on a mid-range computer equipped with a capture card. From there, it becomes possible to deinterlace whatever [interlaced] source using composite or svideo connection, and scale it to the projector resolution.
Dscaler also allows to change the ratio, to adjust video parameters, to choose between different deinterlacing algorithms. For short, Dscaler is simply mandatory for anyone playing with a home theater computer. I almost forgot, Dscaler is open source and so, totally free"

See a scan of the article.

"Given that todays lcd or dlp projectors are equipped with an svga input capable of displaying an analog (interlaced) signal of 800 by 600 points, it becomes quite easy, thanks to a standard (more than 600mhz) pc, to do some signal processing on it, and to adapt it to match the resolution of the projector's matrix (what an external scaler would do). The interesting point being of bypassing the internal deinterlacing of the projector.

... The first [solution] means connecting a set-top dvd player to the pc using a capture card (using the S-video input). The pc is handling the [webmaster note ; deinterlacing and ..] scaling thanks to a dedicated application (Dscaler). We can thus get rid of a dvd-rom drive and keep the ergonomics of a standard player (remote control etc..) while having full control on the different parameters involved in the scaling."

See a scan of the DScaler related part in the article.